JD 5103 loses power and blows white smoke

I recently bought an '05 5103 with a MX6 rotary cutter, it had 165 hours when I bought, I have put 40 hours on it. I was cutting a 44 acre pasture two days ago when the tractor lost power and started blowing some white smoke from the exhaust. I talked to friend who suggested I change the fuel filter, but after an hour the same situation happened again. I have drained the fuel, changed both the fuel lines, and I still have the same problem. After about an hour of cutting i lose power and the tractor blows white smoke. I have to shut it down for 20-30 then it will crank up fine and run for about an hour and the whole thing starts over again. Any suggestions on what the problem might be?

Re: JD 5103 loses power and blows white smoke

Possible a partially blocked fuel return line. Originally I thought the engine was siezing but you say after a few minutes it starts fine. The one question I have is if you try starting immediately does it crank at normal speed or is it v-e-r-y slow. If it cranks slowly then you might have a motor that's siezing up.